Load-supporting damper unit



March 16, 1965 Filed April 25, 1962 R. J. BROADWELL FGJ.

LOAD-SUPPORTING DAMPER UNIT FIG. 3.

5 Sheets-Sheet 1 ROBERT d. BROADWE LL March 16, 1965 R. J. BROADWELL3,173,671

LOAD-SUPPORTING DAMPER UNIT Filed April 25, 1962 3 Sheets-Sheet 2 FIGA.

,'.fnumc l sa DASH BOARD no /TRUNK r-LooR LJ/r |o INVENTOR.

ROBERT .|.aRoAowr-:LL

ATTORNEYS March 16, 1965 R, J. BRoADwl-:LL 3,173,671

LOAD-SUPPORTING DAMPER UNIT Filed April 25, 1962 3 Sheets-Sheet 3 lasINVENTOR.

ROBE RT J. BROADWELL ML f Mu United States Patent O 3,173,671LAD-SUPPRTNG DAMPER UNET Robert 5. Broadweli, Cleveland, hio, assigner,by mesne assignments, to Maremont Corporation, Chicago, lll., acorporation of Illinois Filed Apr. 25, 1962, Ser. No. 190,106 4 Claims.(Cl. 267-64) This invention relates to vehicle suspensions and moreparticularly to load supporting damper units of 'the type disclosed inmy copending applications Serial No. 850,- 957, liled November 4, 1959,now Patent No. 3,083,026 and Serial No. 859,613, tiled lDecember 15,1959, now Patent No. 3,140,098. This application constitutes acontinuation-impart of both of the above mentioned copendingapplications.

In my copending applica-tion Serial Number 850,957, there is disclosed aload supporting damper assist unit which may be conveniently mountedbetween the sprung and uri-sprung masses of a vehicle to provide a loadsupporting assist to the normal springs between such masses and also toprovide the necessary damping action or energy absorption during therelative movement between the masses. The load supporting portion of theunit includes both a variable volume air chamber and a variable volumehydraulic chamber; ,the chambers being separated by a resilientsleeve-like diaphragm.

Also disclosed in my copending application Serial No. 856,957 is acomplete suspension system wherein a plurality of the units previouslydescribed may be utilized in lieu of the conventional springs of thevehicle. Under such circumstances, the damper portion of each unit isutilized as a pump to supply high pressure hydraulic iluid to areservoir or accumulator in response to the relative movements betweenthe sprung and un-sprung masses of the vehicle during operation. Thehigh pressure hydraulic fluid in the reservoir is utilized in turn tomaintain the sprung mass of the vehicle at a desired predetermined levelor height with respect .to the unsprung mass by means of a suitablelevelling valve. This selflevelling function of the system is achievedby introducing and exhausting hydraulic fluid into and out of thehydraulic chambers of the individual load-supporting damper units.

In my later tiled copending application Serial No. 859,613, there isdisclosed a system embodying two loadsupporting damping units of thetype previously described in which the height of the sprung mass of thevehicle is controlled by introducing and exhausting air under pressureinto and out of the air chamber of each unit rather than hydraulic iiuidinto and out of the hydraulic chamber thereof.

The construction of the load supporting damping units disclosed in theabove applications are highly advantageous in that they are moreversatile and can be used in both variable air and variable hydraulicfluid systems. Where such units are utilized solely in a variable airsystem it is possible to eliminate the resilient sleeve-like diaphragmwhich separates the variable air chamber from the variable hydraulicfluid chamber; and, in eiect, eliminate the variable hydraulic fluidchamber from the unit.

An object of the present invention is to provide a load supportingdam-per unit having a variable volume load supporting air chambertherein which is of simplified construction and which may be readilyutilized in a levelling-type suspension system or as an individualassist unit.

Another object of lthe present invention is the provision of an improvedpneumatic system for actuating a plurality of load-suport damper unitsto maintain the 3,173,57l Patented Mar. 16, 1965 sprung mass of avehicle at a substantially predetermined height with respect to theunsprung mass thereof.

These and other objects of the present invention will become moreapparent during ,the course of the following detailed description andappended claims.

The invention may best be understood with respect to the .accompanyingdrawings wherein illustrative embodi` ments are shown.

ln the drawings:

FlGURE 1 is an elevation View, generally in section, of a combinationair spring-shock absorber assembly according to the present invention;

FIGURES 2 and 3 are views taken along lines 2-2 and 3 3, respectively,in FIGURE 1;

FIGURE 4 is a diagrammatic view showing the assembly in FIGURE l mountedto the rear axle of a vehicle;

FGURE 5 is an elevation view of a modied pneumatic circuit; and

FlGURE 6 is a diagram-atie elevation view of still another pneumaticcircuit.

FXGURE 7 is a diagrammatic elevation view of a further pneumatic circuitaccoring to this invention, operative. -to supply air pressure generatedfrom the vehicle engine.

Referring now to FIGURE 1, there is shown a load supporting damper unit10 which includes an air spring assembly 12 and a damper assembly 14mounted therein. The air spring assembly l2 includes an outer tubularcasing mem-ber or housing 16 defining an air chamber 13 whichconstitutes the air spring of the unit. The upper end of the outercasing 16 is joined, as by welding or the like, to an end closure member20. The opposite open end of the outer casing member 16 has a peripheraltapered portion Z2; and, Welded to the tapered portion 22 is acylindrical inner tubular casing member 2-4. Mounted for longitudinal ortelescoping movement relative to the inner tubular member 24 is atubular casing member or plunger 26 forming a part of the damperassembly 14.

Connected between the adjacent ends of the tubular plunger member 26 andVthe inner tubular member 24 is a folded, rolling sleeve-type seal 28which seal is preferably made of flexible material such as corded rubberor the like; however, other flexible materials may be utilized, as isapparent. The essential characteristics of the sleeve type seal 28 arethat it is impervious to air, capable of being folded :or rolled, andrelatively nonresilient, so that it will not expand to any considerableextent under pressure.

The outer end of the sleeve 25 is rigidly secured to the inner tubularmember 24 by `a metal clamping ring 30. The opposite end of the foldedsleeve 28 is fixedly secured to the inner end of the tubular plungermember 26 as by a metal clamping ring 32. In this regard, the respectiveends of the inner tubular member 24 and the plunger member 26 areoppositely bent as at 34 and 36, respectively, to provide an enlargedrecess for engagement of the rings 30 Iand 32 with the respective endsot the sleeve 2S. The sleeve is folded between its secured ends, asmentioned, one ply of the fold engaging the interior surface of theinner tubular casing member 24 and the other ply of the fold engagingthe exterior surf-ace ofthe tubular plunger member 26.

The damper assembly 14 of the unit 10 also includes a cylinder member 3Smounted in spaced concentric relation to the plunger member 26 so as todeiine therewith an annular replenishing chamber 39. @ne end of thecylinder member 3S is iixedly secured to an end plate 40 which definesone end of a damper chamber 41 within the cylinder member. The end plated0, in turn, is secured aire-,er1

`cup-shaped configuration and abuts the end of the end plate about itsinner peripheral wall. The outer peripheral wall of the cover plate 42is joined to the adjacent end 44of the plunger member 26', completingthe connection.

The end plate 40 is'provided with an aperture 46 having a recess therein-forreceiving a flanged stem member 4S which extends through theaperture in spaced apart relationship and has slidably mounted thereonan apertured disc valve Si). A coil spring 52 serves rto resilientlyurge the ydisc valve 5l) into engagement with the annular surfacesurrounding the inner end of the aperture 46, having its upper end inengagement with the disc valve while its lower end .is in engagementwith a flange member 54 fixed to the lower end of the stem member 48.The stem member 48 has -a longitudinal bore 56 formed in the upper endthereof communicating with aV transverse compression passage 58which'extends radially to the outer periphery of `the stem member 48 Iata position above the disc valve Si).

The end plate 4f) also has an aperture 60 formed therein whichterminates in an upwardly facing frustro-conical valve seat 61. Areplenishing valve having :a head 62 is disposed adjacent the valve seat61 'and la stem 64 extend- :ing downwardly therefrom throughthe aperture6d. A conical coil spring 66 resiliently urges the replenishing valve 62into engagement with the valve seat, its upper base end being inengagement with the end plate 4) :and its lower end being in engagementwith a flange formed on the lower extremity of the stem 64. Suitablepassages 65 are formed inthe end plate 44) to provide communica- ,tionwith the replenishing chamber 39.

Mounted within the cylinder member 3S, is a valvcd piston, generallyindicated at 70, which includes -a piston body 72 having a lower hollowportion formed with a peripheral surface for engaging the interior ofthe cylinder member 38, and a reduced upper portion 73. The upperportion 73 of the piston 72 is interiorly threaded :to receive the lowerend of a piston rod 74, the upper end of the rod 74 being fixed to thecentral interior lof the closure member 20. The piston rod 74 has atransverse passage 75 communicating with a longitudinal passage 76extending to the lower end thereof. Y

Extending radially through the lower portion of the piston body 72 is aplurality :of circumferentially spaced compression passages 77. Thecute-r periphery of the lower portion of the piston body 72 adjacent thepassages r77 isrrelieved, as indicated at 78, to permit the fluidflowing through the passages 77 to move axially upwardly therefrom. Thismovement of the fluid is controlled by an O-ring 80 of a diametersutiicient to engage the inner periphery of the cylinder member 38. TheO-ring 80 is Ymounted 4between an upper carrier ring 82 of angularcross-sectional configuration and a lower sealing ring 84 arranged toengage 'an upwardly facing annular seating surface 86 formed on thepiston body between the lower portion and the reduced upper portionthereof. The lower sealing ring 84 is resiliently urged into engagementwith the seating surface 86 by means of a coil spring 88 surrounding thereduced upper portion 73 of the piston body 72. The'lower end of thespring 88 engages the carrier ring Y82 and the upper end thereof engagesa notched washer 90 mounted between the lower end ofthe piston rod 74and the upper extremity of the upper portion 73 of the piston body'72.

The lower end 94 of the axialpassage in the 4rod 74 is arranged to beclosed by means 4of disk valve 96. The disk valve is centrally aperturedto receive Ia guide member 98 Vwhich is fixed to the lower end portionof the valve body 72, as by an apertured disk 10i). The -disk valve 96is -resiliently urged int-o Aengagement with the annular surfaceadj-acent the opening 94 by means of a coil spring 102 mounted betweenthe disk valve 96 and the apertured disk A resilient packing ring 104 isslidably carried in sealing engagement with the piston rod 74. Acup-shaped annular plug 106 is positioned between the rod 74 and theinterior peripheral end of the plunger member 26, this plug yalsoengaging the exterior peripheral surface of the resilient packing ring184. A tapered compression spring 108 is nested within the plug 106,:and an `oppositely tapered compression washer 110 is lpositioned at the.apex of the spring 108. The flexible packing ring 104 is seated with'its lower tapered surface against the compression washer 118, and theplug 166 is closed by a cap 112 which engages the opposite upper taperedsurface of the flexible packing ring 184. The plug 166 is peripherallyrecessed along its free end, :as at 114, and receive an O-ring 116.Likewise, the plug 106 has transverse passages 118 communicating withthe lower end of the cup-shaped recess, and the replenishingchamber 39.The cap 112 hasV a peripheral shoulder for fixing the O-ring, as isapparent. The cap 112 is maintained in fixed engagement with the plug106 by an inwardly turned flange 122 carried by the end of the plungermember 26.

Welded to the closure member 20 of the outer casing 16 (whichconstitutes the upper end of the unit 10) is van eyeconnector 124, while.a stem connector 126 is rigidly secured to the opposite, lower endplate `42.

As will be apparent, the load supporting damper unit 18 is adapted toreplace the conventional shock absorbers of vehicles, the damperassembly 14vacting as an energy absorber, while the air spring assembly12 is adapted to resiliently support a portion of the sprung mass of thevehicle on the unsprung mass thereof. The upper housing 16 carries aconventional-tire valve 128 in communication with the air chamber 18 ofthe unit 1f) to enable vthe air pressure within the air chamber to bevaried.

Assembly of the elements is simplified by virtue of the fact the foldedsleeve first is joined to the inner casing member 24 and plunger member26, and this assembly is inserted as a unit into the outer casing member16. The tapered end of the outer casing member 16 is then convenientlyjoined to the inner casing member 24, as by welding, to providetanair-tight joint.

Referring now-to FIGURE 4, an exemplary mounting arrangement for-theunit 10 is shown in assembled relationship with a vehicle 130. Thevehicle 130 `has a sprung mass 132, which includes the transverseunderframe of the vehicle. The vehicle 130 conventionally has anunsprungzmass 134 which includes a rear axle136 and associated tires138. The rear springs and the vehicle 130 are conventionally joined tothe axle 136 by U-bolts 142. Joined to the underside of the U-bolt 142is a bracket plate 144 having a downwardly inclined lip 146. Thetransverse underframe of the vehicle 130 carries'longitudinallyextending studs 148 adapted to receive the eye-connector 124 of the unit14B. Also, the stem connector 126 of the unit 10 is joined to the lip146 of the bracket plate 144 in inclined relationship, this being awell-known arrangement for mounting conventional shock absorbers tovehicles.

In the assembly shown in FIGURE 4, aflexible air hose 150 is connectedat its one end to the casing 16 of the unit 10, while the opposite endis in operative communication with a conveniently accessible air fillingstation, for example, the floor of an automobile trunk. The tire valve128, in this instance, is joined to the air `hose 150 and is fixed tothe trunk floor. Numerous alternative mounting Vpositions for the tirevalve 128 will be apparent to those skilled in the art; the arrangementshown in FIGURE 4 is, however, convenient for garage replacementpurposes with used automobiles, as by a mechanic.

In operation, it willbe understood that the-air pressure within the airchamber 18 will determine the level or height of the frame 132 withrespect to the axle assembly 136 under static conditions. Where severestatic Vloads are placed on the frame 132, such as several pieces ofluggage in the trunk, a trailer hitched to the rear bumper Vor the like,there may be a tendency for the frame 132 to ride too low to the axleassembly resulting in the rear overhang of the vehicle scraping thepavement in driveways or the like, a ride in which the frame bottoms outtoo often, and/or a situation in which the light beams of the vehicleare directed too far upwardly. With the present units mounted betweenthe frame and axle assembly it is necessary merely to attach aconlventional air hose, such as found in any tilting station,

to the valves 128 to introduced air into the air chambers 18 suliicientto raise the frame 132 to a level which appears to be satisfactory uponvisual inspection. Gf course, when the excessive static loads areremoved, the frame 132 can be lowered to a more desirable level bysimply actuating the tire valves to allow an appropriate amount of airto escape from the air chamber 13 of each unit.

Under dynamic conditions when the vehicle is in motion, it will beunderstood that the air spring assembly 2 of each unit serves to addresilient support to the frame 132 in addition to the support providedby the springs 14). The cylindrical casing member Z6 acts as a plungerWithin the air chamber which extends and contracts the air chamber inresponse to extension and contraction .of the entire unit as a result ofthe relative movements between the frame and the axle assembly.

Moreover, the damper assembly 14 or each unit absorbs the excessiveenergy resulting from the relative movements of the frame and axleassembly and serves to dampen these relative movements by controlledrestriction of the hydraulic iluid within the damping chamber 41. Incompression, the flow of fluid Within each damping chamber is past thedisk valve 54 from the lower portion of the chamber to the upper portionthereof. The excess hydraulic fluid, which is equal to the piston roddisplacement, passes from the bottom portion of the damping chamber intothe replenishing chamber 39 past the valve St?. On rebound, hydrauliciluid from the upper portion of each damping chamber flows through thepassage 75 past the valve 96 and into the lower portion of the dampingchamber and sufficient hydraulic fluid to replace the piston roddisplacement is drawn into the lower portion of the damping chamber fromthe replenishing chamber past the replenishing valve 62.

It will be understood that the unit 16 of the present invention may bereadily utilized in a selfleveling system of the type disclosed in mycopending application Serial No. 859,613. Such a system is shownschematically in FIGURE wherein the air hose 159 for the unit 1t),constituting the left-hand unit of the system, is connected to a T-tting152. r:The T-ftting also receives an air hose 159 from an identicalright-hand unit 1G'. An air hose 154 is also connected to the T-tittingand to a lockout position sensitive three-way leveling valve mechanism156 of a construction similar to the comparable valve mechanismdisclosed in my co-pending application Serial No. 859,613 which ishereby incorporated by reference into the present disclosure.

The valve mechanism 156 also has connected therewith a high pressureline or air hose 15S and a low pressure or exhaust line or air hose 16u,both of which are in turn connected to a tilling and exhaust valvemechanism 162 which also is of a construction similar to the comparablevalve mechanism disclosed in my co-pending application Serial No.859,613. As disclosed in my above mentioned co-pending application,valve mechanism 162 includes a cap which acts as a valve to close theexhaust line 16@ which ultimately has the elect of locking out theleveling valve mechanism 156. The valve mechanism 162 also includes aconventional tire valve which can be connected to a conventional fillingstation type air hose.

The arrangement can be appropriately modied by providing a pressure tank164 in parallel with the high pressure line 158, as by a line or airhose 166. The provision of the tank 164 permits the system to elevatethe frame 132 at any time rather than requiring an immediate trip to thefilling station. The tank 164 can then be refilled at the fillingstation at a more convenient time.

FIGURE 6 discloses another arrangement in which the amount of levelingof the system is determined by visual inspection rather than by anautomatically operable positio-n sensing valve mechanism. The systemdiiers from that shown in FGURE 4 in that it embodies an air pressuretank 164, such as that shown in FIGURE 5, which is connected, as by aline or air `hose 170, with: a conventional three-way valve 16S of anysuitable construction conveniently mounted on the vehicle, yas on thedash board or the like. The valve 168 includes an exhaust port inaddition to the port connected with the tank 164 and a third port whichis connected with the T-tting 152 in series with a minimum pressurecheck valve 172, as by lines 174 and 176.

The check valve 172 merely serves tot prevent the air pressure withinthe air chambers 1S `of the units from going below a predeterminedminimum value. The valve mechanism 16S is normally maintained in a nullposition in which all o the ports are closed oli. When moved in onedirection the air chambers 18 of the units are communicated with theatmosphere so as to permit the frame 132 to be lowered relative to theaxle assembly 134. When the valve 16S is moved in the opposite directionthe air chambers 1S of the units are communicated with the tank 164 sothat the frame 132 can be raised relative tothe axle assembly 134.

The present units m-ay also be utilized in a self-leveling system whichis operable not only under static conditions but under dynamicconditions as well, by the provisions of a continuous source ofcompressed air in lieu of the exahustable source 164i disclosed in thearrangement shown in FEGURE 5. Such a system is disclosed in FIGURE 7and it will be noted that there is provided a pump assembly 175i` whichis preferably constructed in accordance With the teachings of OsburnPatent 2,630,102 issued March 3, 1953. As disclosed in the Osburn patentthe inlet of the pump 178 is adapted t-o be connected to the suctionmanifold of the internal combustion engine of the vehicle, as by a line179. The pump includes two parallel outlet lines 180 which areinterconnected as by a T-ntting 182. The T-tting 182 is, in turn,connected to the high pressure line 158 extending from the levelingvalve mechanism 156 in lieu of the connection to the valve mechanism 162previously described in connection with the arrangement shown in FIGURE5. The exhaust line 1611 of the leveling valve mechanism 156 extends toa simple, two-way valve 18d which is operable either to permit the line164i to exhaust to atmosphere or to be closed off so as to lock out theleveling valve mechanism 156. It will be noted that with the systemshown in FIGURE 7, automatic selfdeveling of the frame 132 with respectto the axle assembly 134 can be obtained either continuously o-rselectively. It it is desired to lock out the leveling valve mechanismso that it will not operate under dynamic conditions, the valve S4 ismoved to close olf the exhaust line 16u which has the ultimate etfect oflocking out the leveling valve mechanism. On the other hand, the valve184 may be moved to an open position permitting the line 160 to exhaustto atmosphere in which case the leveling valve mehcanism Willautomatically function to properly maintain the level of the frame 132so long as the engine of the vehicle is in operation to provide powerfor the pump 178 which supplies the source of air under pressure toeiect raising movements of the frame. As indicated above, it is notnecessary to lock out the leveling valve during actual operation of thevehicle since the pump 178 is capable of supplying a continuous sourceof air under pressure so long as the engine of the vehicle is operating,even though it is preferred to lock out the valve mechanism during theactual movement of the vehicle.

'Z7 t Y Insofar as the operation of the pump E73 is concerned, anadequate disclosure thereof can be obtained by referring to theabove-mentioned Osburn patent. For present purposes suiiice it to saythat the pump acts essentially as a demand pump. That is, so long asthere is a predetermined pressure maintained in the line F58, the pumpwill not operate. However, as soon as this pressure is reduced by thedemand of the units 10 and 10', pump 178 will automatically begin tofunction to raise the pressure back to its desired level and suchpressure will be continuously available as demanded so long as theengine is running.

It thus will be seen that the objects oi this -invention have been fullyand effectively accomplished. it will be realized, however, that theforegoing speciiic embodiment has been shown and described only for thepurpose of illustrating the principles of this invention and is subjectto extensive change without departure from such principles. Therefore,this invention includes all modifications encompassed within the spiritand scope of the following claims.

What is claimed is:

l. A load supporting damper unit adapted to be connected between thesprung .and unsprung masses of a vehicle comprising: a rigid outertubular member open at one end and closed at the other; a rigid openended cylindrical member tixedly secured at one end to the open end ofsaid outer tubular member and extending therein; a cylinder memberdefining a hydraulic damping chamber therein; a piston siidably engagedwithin said cylinder member; a piston rod extending from one side ofsaid piston outwardly of said cylinder member and having its outer endsecured to said outer tubular member; a tubular casing member disposedin surrounding relation to said cylinder member and movable therewithtelescopically within said cylindrical member and said outer tubularmember, said casing member defining with said cylinder member an annularhydraulic replenishing chamber; means interconnecting one of the ends ofsaid cylinder and casing members for permitting controlled restrictedflow of hydraulic fluid between said damping and replenishing chambersin response to the sliding movement of said piston within said cylindermember; means interconnecting the other ends of said cylinder and casingmembers for providing a duid-tight seal between the portion of saidpiston rod extending outwardly from said cylinder and casing members andsaid damping and replenishing chambers; means carried by said piston forpermitting controlled restricted flow of hydraulic duid Within saiddamping chamber on opposite sides of said piston in response to thesliding movement Vof said piston within said cylinder member; a sleeveof flexible, iluid impervious material mounted in folded relationbetween the exterior periphery of said casing member and the interiorperiphery of said cylindrical member, said lsleeve having one endthereof secured to the inner end of said casing member and the other endthereof Vsecured to the other end of said cylindrical member, theportion of the sleeve extending between the one end thereof and the foldtherein being disposed in engagement with the exterior periphery of saidcasing member and the portion of the sleeve extending betweentheopposite end thereof andthe fold therein being disposed in engagementwith the interior periphery of said cylindrical member; the exteriorperipheries of said cylindrical member, said sealing means, and theportion of said piston rod extendingoutwardly of said sealing meansA andthe interior peripheries of said sleeve and said outer tubular memberdefining a load supporting air chamber Variable in volume in response tothe telescopic movements of said cylinder and casing members within saidcylindrical and outer tubular members; and means for permitting airunder pressure to beintroduced into and exhaustedfrom said air chamber.

2. A'load supporting damper unit as deiined in Vclaim l wherein innerend of said cylindrical member includes an enlarged offset portion, anda rigid ring xedly securing the opposite end of said sleeve between thesame and the offset portion of said cylindrical member. Y

3. A load supporting damper unit as delined in claim 2 wherein theopposite Vend of said casing member includes a reduced offset portion,and a rigid ring xedly securing the one end of said sleeve between thesame and the offset portion of said casing member. Y

4. A load supporting damper unit as defined in claim 1 wherein said lastmentioned means comprises a tire Valve mounted in said outer tubularmember in communication with said air chamber.

References Cited in the tile of this patent UNITED STATES PATENTS3,000,400 Cislo V Sept. 19, l96l

1. A LOAD SUPPORTING DAMPER UNIT ADAPTED TO BE CONNECTED BETWEEN THESPRUNG AND UNSPRUNG MASSES OF A VEHICLE COMPRISING: A RIGID OUTERTUBULAR MEMBER OPEN AT ONE END AND CLOSED AT THE OTHER; A RIGID OPENENDED CYLINDRICAL MEMBER FIXEDLY SECURED AT ONE END TO THE OPEN END OFSAID OUTER TUBULAR MEMBER AND EXTENDING THEREIN; A CYLINDER MEMBERDEFINING A HYDRAULIC DAMPING CHAMBER THEREIN; A PISTON SLIDABLY ENGAGEDWITHIN SAID CYLINDER MEMBER; A PISTON ROD EXTENDING FROM ONE SIDE OFSAID PISTON OUTWARDLY OF SAID CYLINDER MEMBER AND HAVING ITS OUTER ENDSECURED TO SAID OUTER TUBULAR MEMBER; A TUBULAR CASING MEMBER DISPOSEDIN SURROUNDING RELATION TO SAID CYLINDER MEMBER AND MOVABLE THEREWITHTELESCOPICALLY WITHIN SAID CYLINDRICAL MEMBER AND SAID OUTER TUBULARMEMBER, SAID CASING MEMBER DEFINING WITH SAID CYLINDER MEMBER AN ANNULARHYDRAULIC REPLENISHING CHAMBER; MEANS INTERCONNECTING ONE OF THE ENDS OFSAID CYLINDER AND CASING MEMBERS FOR PERMITTING CONTROLLED RESTRICTEDFLOW OF HYDRAULIC FLUID BETWEEN SAID DAMPING AND REPLENISHING CHAMBERSIN RESPONSE TO THE SLIDING MOVEMENT OF SAID PISTON WITHIN SAID CYLINDERMEMBER; MEANS INTERCONNECTING THE OTHER ENDS OF SAID CYLINDER AND CASINGMEMBERS FOR PROVIDING A FLUID-TIGHT SEAL BETWEEN THE PORTION OF SAIDPISTON ROD EXTENDING OUTWARDLY FROM SAID CYLINDER AND CASING MEMBERS ANDSAID DAMPING AND REPLENISHING CHAMBERS; MEANS CARRIED BY SAID PISTON FORPERMITTING CONTROLLED RESTRICTED FLOW OF HYDRAULIC FLUID WITHIN SAIDDAMPING CHAMBER ON OPPOSITE SIDES OF SAID PISTON IN RESPONSE TO THESLIDING MOVEMENT OF SAID PISTON WITHIN SAID CYLINDER MEMBER; A SLEEVE OFFLEXIBLE, FLUID IMPERVIOUS MATERIAL MOUNTED IN FOLDED RELATION BETWEENTHE EXTERIOR PERIPHERY OF SAID CASING MEMBER AND THE INTERIOR PERIPHERYOF SAID CYLINDRICAL MEMBER, SAID SLEEVE HAVING ONE END THEREOF SECUREDTO THE INNER END OF SAID CASING MEMBER AND THE OTHER END THEREOF SECUREDTO THE OTHER END OF SAID CYLINDRICAL MEMBER, THE PORTION OF THE SLEEVEEXTENDING BETWEEN THE ONE END THEREOF AND THE FOLD THEREIN BEINGDISPOSED IN ENGAGEMENT WITH THE EXTERIOR PERIPHERY OF SAID CASING MEMBERAND THE PORTION OF THE SLEEVE EXTENDING BETWEEN THE OPPOSITE END THEREOFAND THE FOLD THEREIN BEING DISPOSED IN ENGAGEMENT WITH THE INTERIORPERIPHERY OF SAID CYLINDRICAL MEMBER; THE EXTERIOR PERIPHERY SAIDCYLINDRICAL MEMBER, SAID SEALING MEANS, AND THE PORTION OF SAID PISTONROD EXTENDING OUTWARDLY OF SAID SEALING MEANS AND THE INTERIORPERIPHERIES OF SAID SLEEVE AND SAID OUTER TUBULAR MEMBER DEFINING A LOADSUPPORTING AIR CHAMBER VARIABLE IN VOLUME IN RESPONSE TO THE TELESCOPICMOVEMENTS OF SAID CYLINDER AND CASING MEMBERS WITHIN SAID CYLINDRICALAND OUTER TUBULAR MEMBERS; AND MEANS FOR PERMITTING AIR UNDER PRESSURETO BE INTRODUCED INTO AND EXHAUSTED FROM SAID AIR CHAMBER.